1. Field of the Invention
The present invention relates to a magnetic head for perpendicular recording and a method for manufacturing the same, and a magnetic disk storage apparatus mounting the magnetic head for perpendicular recording.
2. Description of the Related Art
In a magnetic disk storage apparatus, the data on a recording medium is read and written by a magnetic head. The areal recording density is required to be increased in order to increase the recording capacity per unit area of the magnetic disk. However, with a current longitudinal recording method, there occurs a problem as follows. As the length of a bit to be recorded decreases, thermal fluctuation of the magnetization of the medium becomes a serious problem which restricts the limit of the areal recording density. There is a perpendicular recording method for recording a magnetization signal in a direction perpendicular to the medium for solving this problem.
There are two types of perpendicular recording methods: a method in which a double layered perpendicular medium having a soft magnetic underlayer is used as a recording medium; and a method in which a single layered perpendicular medium having no underlayer is used. When the double layered perpendicular medium is used as the recording medium, recording is usually performed by using a so-called single pole type head having a main pole and an auxiliary pole.
Further, in order to improve the recording density, the track density and the linear recording density are required to be improved also for perpendicular recording. In order to improve the track density, the track width of the magnetic head is required to be increased in fineness and precision. When perpendicular magnetic recording using the double layered perpendicular medium and the single pole type head is performed, the distribution of the write field generated from the magnetic pole of the single pole type head is largely different from that of the longitudinal magnetic recording. For example, as shown in FIG. 2(A), the contours of the perpendicular component of the write head field intensity are distributed concentrically wherein the maximum intensity occurs from the central portion of the main pole, and exhibit such a distribution that a contour closer to the outside has a more swollen shape. Therefore, the shape of the air bearing surface of the main pole largely affects the recorded magnetization pattern of the medium.
FIG. 2(A) is a distribution diagram of the contours of perpendicular components of head write field in the form of a main pole in the prior art obtained by simulation. FIG. 2(A) indicates that the field distribution is curved toward the trailing side. Herein, the trailing side denotes the downstream side of the disk rotating direction, and it denotes the direction of the arrow indicated as “disk rotating direction 17” in FIG. 2(A). In contrast, the upstream side of the disk rotating direction is referred to as a leading side. FIG. 2(B) is a diagram showing the magnetization configuration, obtained from simulation, recorded on the medium when a head having such a magnetic field distribution is used. As indicated from FIG. 2(B), the magnetic reversal position in the track central portion is situated more toward the disk rotating direction than in each of the track edge portions, so that the shape of magnetic transition of the medium is curved. Such a phenomenon actually becomes apparent from the observation result by means of a MFM: magnetic force microscopy.